JPH0266984A - Bragg reflection type laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance the coupling efficiency between an active region and a Bragg region and to decrease a waveguide loss in the Bragg reflection region by incorporating a layer wherein the extending part of a quantum well structure is disorganized as a waveguide layer in the Bragg reflection region. CONSTITUTION:The parts of a cap layer 5 and a clad layer 4 other than an active region are etched. Thereafter, ions are implanted into the part other than the active region, and heat treatment is performed. In this way, a quantum well layer 3 in the ion implanted region is broken. A wave pattern 6 whose crests cross the longitudinal direction of the active region is formed at the exposed part of the clad Iayer 4. Then, the region along the light outputting direction in the active region is made to remain, and the wave pattern 6 is etched. This element is provided with the following regions: the region wherein a quantum well structure is provided, i.e., the region wherein the cap Iayer 5 is provided; and the Bragg reflection region wherein the light having the specified wavelength that is incorporated in the output light from the active region, i.e., the region wherein the wave pattern 6 is provided. The Bragg reflection region includes a layer wherein the extending part of the quantum well structure is disorganized as a waveguide layer 3'.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improving the characteristics of Bragg reflection lasers. The present invention is suitable for use as a light source for optical communication and optical measurement.

〔overview〕

The present invention provides a Bragg reflection type laser provided with a quantum well structure, in which the coupling between the active region and the Bragg reflection region is achieved by using a layer in which an extension of the quantum well structure is disordered as a waveguide for the Bragg reflection region. This increases efficiency while reducing waveguide losses in the Bragg reflection region.

[Conventional technology]

Distributed feedback lasers (dis-tribu lasers), which have a periodic structure in their waveguides, are used as lasers with excellent single-mode properties.
ted feedback 1aser) and Bragg reflective laser (distributed Bragg-r
effector 1aser) is expected.

A distributed feedback laser has a periodic structure along its active region, and utilizes Bragg reflection caused by the periodic structure to feed back light in a distributed manner. On the other hand, a Bragg reflection type laser has a periodic structure at the emission end of the active region and causes the emitted light to undergo Bragg reflection.

Distributed feedback lasers have a simple structure and are easy to manufacture.

Further, by using a phase shift, single mode property can be improved.

However, since an uneven light intensity distribution occurs in the resonator,
Produces spatial hole burning. This has resulted in unstable operation at high outputs and increased spectral line width. Another drawback is that motion analysis is complicated.

In contrast, Bragg reflection lasers operate essentially the same as Fabry-Perot lasers and do not produce spatial hole burning. Moreover, the operation is simple and easy to analyze and optimize.

Literature related to Bragg reflection lasers includes (i)
Murata Shigeru, Mido Ikuo and Kobayashi Kolarou, “Spectral Line Talistics for a 1.5μ [0DBR Radhe with Frequency Tuning Region J, IEEE II! Journal of Claontum Electronics Vol. Volume 23, No. 6, June 1987 (Shigeru Murata, Iku.

Mito, and Kohroh Kobaya
shi, “5pectralCharacteri
Sticks for a 1,5μm D
BRLaser with Frequency-Tun
ing Region, IEEE Jour-n
al of Quantum Electronic
s, Vol, Qε-23°No, 6. Ju
ne 1987) (11) Keisuke Kojima, Susumu Noda, Kazumasa
Minaga, Kazuo Kinichima, Koichi Hamanaka, Takashi Nakayama, “Edge and Surface Emitting Distributed Bragg Reflector Laser with Multi-Claontum Well.
"Active/Passive Unive Guide", Applied Physics Letters Vol. 50, No. 5, February 2, 1987 (Keisuke kojima, Susu-m
u Noda, kazumasa Mitsunag
a. Kazuo Kyuma.

Koichi hamanaka, and Tak
ashi nakayama.

“Bdge-and surface-emittin
g distributedBragg reflect
tor 1aser with multiquant
umwell active/passive wav
eguides', Appl.

Phys, Lett, 50(5), 2 FetJr
Uary 1987) etc.

[Problem that the invention seeks to solve]

However, the Bragg reflection type laser has a complicated structure and is difficult to manufacture. In particular, it is important in terms of characteristics to increase the coupling efficiency between the active region and the Bragg reflection region and to reduce the waveguide loss in the Bragg reflection region. However, it has been difficult to achieve both.

For example, the above-mentioned document (i) proposes a Bragg reflection type laser in which a highly absorbing active layer is etched in order to reduce loss in the Bragg reflection region. but,
In this device, since the waveguide structure is different between the active region and the Bragg reflection region, the coupling efficiency decreases.

In addition, in the document (ii), in order to increase the coupling efficiency,
We have proposed a device that uses the same quantum well structure in the active region and Bragg reflection region. This takes advantage of the relatively small absorption of the quantum well structure. However, although the coupling efficiency is high, waveguide loss remains.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a Bragg reflection laser with high coupling efficiency between an active region and a Bragg reflection region and low waveguide loss in the Bragg reflection region.

[Means for solving problems]

The Bragg reflection type laser of the present invention is characterized in that the Bragg reflection region includes a layer in which an extended portion of a quantum well structure is disordered as a waveguide layer.

To manufacture this device, a quantum well structure is formed on a semiconductor substrate, a part of this quantum well structure is left as an active region, and the quantum well structure other than the active region is disordered. A Bragg reflection region is formed in the region along the light output direction of the active region.

In order to disorder the quantum well structure, it is desirable to implant ions into the quantum well structure, followed by heat treatment.

[For production]

The active region and the Bragg reflection region are manufactured with the same quantum well structure, and the Bragg reflection region is disordered. The quantum well structure is destroyed by disordering, and the loss is reduced. Furthermore, the active region and the Bragg reflection region basically have the same structure, so there is no mismatch between the two regions, and high coupling efficiency can be obtained. Therefore, a Bragg reflection type laser having a narrow spectral linewidth and excellent single mode properties can be obtained.

〔Example〕

FIG. 1 shows perspective views of a Bragg reflection type laser according to a first embodiment of the present invention at various manufacturing steps. In this drawing, necessary parts are exaggerated in order to clarify each part of the element and the layer structure.

FIG. 1(a) shows a step of forming a quantum well structure on a semiconductor substrate 1. As shown in FIG. That is, a cladding layer 2 is formed on a substrate 1,
A quantum well layer 3, a cladding layer 4, and a cap layer 5 are epitaxially grown in this order.

The quantum well layer 3 is a single quantum well or a multiple quantum well,
SCH (Separated Config) on both sides
nementHetero-3structure) layer. The thickness of the quantum well is 20 to several 100 layers, and the thickness of the entire quantum well layer 3 is about 2000 to 5000 layers.

Steps (b) and (C) show a step of leaving a part of the quantum well structure as an active region and disordering the quantum well structure in a portion other than the active region.

In this embodiment, after the active region is formed in the steps shown in FIG. 1 et al., the quantum well structure is disordered in the step shown in FIG. 1(C).

That is, a mask is provided on the cap layer 5, and the cap layer 5 and a portion of the cladding layer 4 are etched in areas other than the active region. After this, ion implantation is performed in parts other than the active region, and then heat treatment is performed. As a result, the l-well layer 3 in the ion-implanted region is destroyed.

FIGS. 1(d) and (e) show that in the disordered region,
3 illustrates the process of forming a Bragg reflective region along the light output direction of the active region. In this step, a waveform 6 whose peaks are perpendicular to the length direction of the active region is formed on the exposed portion of the cladding layer 4, and then a waveform 6 is formed leaving a region along the light output direction of the active region. etching.

As a result, the Bragg reflection type laser shown in FIG. 1(e) is obtained.

FIG. 2 shows a cross-sectional view along line AA' in FIG. 1(e), ie, a cross-sectional view along the active region and the Bragg reflection region.

This element consists of an active region provided with a quantum well structure, that is, a region provided with a cap layer 5, and a Bragg reflector that reflects light of a specific wavelength included in the output light from this active region and returns it to the active region. A reflective region, that is, a region provided with a waveform 6. The Bragg reflection region includes a layer in which the extension of the quantum well structure is disordered as a waveguide layer 3'.

FIG. 3 shows perspective views of a Bragg reflection type laser according to a second embodiment of the present invention at various manufacturing steps. Similar to FIG. 1, this drawing also exaggerates necessary parts in order to clarify each part of the element and the layer structure.

This embodiment differs from the first embodiment in that a waveform 6 for Bragg reflection is provided between the cladding layer 4 and the waveguide layer 3'.

FIG. 3(a) shows a step of forming a quantum well structure on the semiconductor substrate 1. FIG. In this embodiment, the quantum well layer 3
A guide layer 9 is grown on top of the cladding layer 4 at this stage.
This embodiment differs from the first embodiment in that the cap layer 5 is not grown.

FIG. 3(b) shows a step of leaving a part of the quantum well structure as an active region and disordering the part of the quantum well structure other than this active region. That is, a mask 7 is provided in a region where an active region is to be formed, ion implantation is performed, and then heat treatment is performed.

As a result, the quantum well structure in the portion where the mask 7 is not provided becomes disordered. After this, the mask 7 is removed.

FIG. 3C shows the step of forming a Bragg reflection region in the disordered region along the light output direction of the active region. That is, the guide layer 9 in the portion that becomes the Bragg reflector
A wave pattern 6 is formed.

In the step shown in FIG. 3(d), a cladding layer 4 and a cap layer 5 are epitaxially grown on the guide layer 9. As shown in FIG.

In the step shown in FIG. 3(e), waveguides are formed in the active region and the Bragg reflection region. That is, etching is performed leaving a region that will become a waveguide.

In this way, a Bragg reflection type laser equivalent to that of the first embodiment is obtained.

In the above embodiments, an example has been described in which Bragg reflective regions are provided on both sides of the active region, but it is also possible to provide Bragg reflective regions only on one side of the active region.

FIG. 4 shows a perspective view of a Bragg reflection type laser according to a third embodiment of the present invention, and FIG. 5 shows a sectional view taken along line BB' in FIG. In this embodiment, the present invention is implemented in a variable frequency laser.

This element includes an active region provided with a quantum well structure, a Bragg reflection region that reflects light of a specific wavelength contained in output light from the active region and returns it to the active region, and further includes an active region and a Bragg reflection region. A phase adjustment region is provided between the reflection region and the reflection region.

The active region includes a substrate 1, a cladding layer 2, a quantum well layer 3, a cladding layer 4, and a cap layer 5, and oscillation electrodes 11.
12 are provided.

The phase adjustment region includes a substrate 1, a cladding layer 2, and a quantum well layer 3.
comprises a disordered waveguide layer 3' and a cladding layer 4. Furthermore, phase adjustment electrodes 13 and 14 are provided on the back side of the substrate 1 and on the surface of the cladding layer 4, respectively.

The Bragg reflection region includes a substrate 1 , a cladding layer 2 , a waveguide layer 3 ′ in which a quantum well layer 3 is disordered, and a cladding layer 4 . The cladding layer 4 is provided with corrugations 6. Moreover, electrodes 15 and 16 for wavelength sweeping are provided on the back side of the substrate 1 and on the surface of the corrugated pattern 6, respectively.

In the above embodiments, the case where a ridge type waveguide structure is used is explained as an example, but the present invention can be similarly implemented with a rib type or embedded type. Furthermore, the present invention can be implemented similarly even if the quantum well structure is disordered without using ion implantation.

As a method other than ion implantation, for example, thermal diffusion can be used.

〔Effect of the invention〕

As described above, the Bragg reflection laser of the present invention has high coupling efficiency between the active region and the Bragg reflection region, and low waveguide loss in the Bragg reflection region. Therefore, the reflectance of the Bragg reflection region can be increased, and wavelength selectivity can also be improved. This has the effect of narrowing the spectral line width of the Bragg reflection laser and improving single mode properties.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of each manufacturing process of a Bragg reflection type laser according to a first embodiment of the present invention. FIG. 2 is a sectional view taken along line AA' in FIG. 1(e). FIG. 3 is a perspective view of a Bragg reflection type laser according to a second embodiment of the present invention at various manufacturing steps. FIG. 4 is a perspective view of a Bragg reflection type laser according to a third embodiment of the present invention. FIG. 5 is a sectional view taken along line BB' in FIG. 4. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Cladding layer, 3... Quantum well layer, 3'... Waveguide layer, 4... Cladding layer, 5...
Cap layer, 6...Wave type, 7, Death...Mask, 9...
- Guide layer, 11-16...electrode. Patent Applicant Optical Measurement Technology Development Co., Ltd. Agent Patent Attorney Naotaka Ide

Claims (1)

[Claims] 1. An active region provided with a quantum well structure, and a Bragg reflection region that reflects light of a specific wavelength included in output light from the active region and returns it to the active region. A Bragg reflection type laser, wherein the Bragg reflection region includes a layer in which an extension of the quantum well structure is disordered as a waveguide layer. 2. A step of forming a quantum well structure on a semiconductor substrate, a step of leaving a part of this quantum well structure as an active region, and making the quantum well structure in a part other than this active region disordered; and this step makes the quantum well structure disordered. forming a Bragg reflection region along the optical output direction of the active region in the area formed by the active region. 3. The method of manufacturing a Bragg reflection type laser according to claim 2, wherein the step of disordering the quantum well structure includes the step of implanting ions into the quantum well structure, and the step of performing heat treatment after this step.